In the prior art, various connection elements are known which connect at least two pre-punched components with each other. A proven approach is to insert a threaded bolt through the component openings and to fasten the components to each other by screwing a nut onto the threaded bolt. But this requires an accessibility of the connection from both sides, which is not always given.
Therefore, WO 2007/134588 A1 proposes a spring screw, which consists of a regularly wounded wire coil with closely spaced or abutting adjacent wire windings. Only by means of this winding arrangement, which is also based on a rigid and non-flexible spring wire, it is possible to produce a thread-like outer contour of the spring screw. At one end of the wire coil, the wire is wound into a flat spiral so that a head-like construction results. The other end of the wire coil has an installation web protruding radially into the coil and by means of which the spring screw is screwed into a component opening. This spring screw is intended for swinging, creeping, setting or generally deformable materials. While screwing the spring screw into the component opening, a thread groove is cut into the radially inner wall of the component opening. Therefore, this spring screw works on the principle of a self-cutting screw, only that it is produced with lower geometric requirements particularly with regard to the formation of a thread. Due to this screw function, the installation effort for this spring screw is great on the one hand, because it is time-consuming to screw it into the component opening. Furthermore, the material of the spring screw has to be adjusted to the component material so that in fact the spring screw can cut a thread groove into the component material. Otherwise this spring screw does not provide any grip in the component opening. It is disadvantageous that the spring screw must be produced with high accuracy so that the spring screw can be kept in the regularly cut thread groove.
WO 2012/084385 A1 describes a cutting spring attachment which is mounted onto a screw. Here, it is already a disadvantage that the connection element is constructed in two parts, since it consists of a screw and a cutting spring attachment. Furthermore, also the installation effort is time-consuming, because the screw has to be screwed into the component opening with care and by cutting a thread.
WO 2011/053170 describes a plurality of connection elements which either are wound from a wire to a wire coil or which comprise at least one wire coil portion between a massive head and a massive end or tip portion of the connection element. The connection elements described herein have a flat radially outer side or a radially outer side consisting of rounded subsections. This configuration of the radially outer side supports a press fit of the connection elements in a component opening, wherein the connection element pushes the radially outer side against the component wall of the bore due to the outwardly directed radial spring forces. This inner radially directed spring forces as well as a torsional stiffness and an axial stability of the disclosed connection elements are achieved especially by means of a tight winding of the wire coil. At this, essentially the adjacent windings abut each other. The connection elements described herein are compressible in radial direction, but not deformable in the axial direction. Once the connection element has been forced into a component opening by means of a radial compression, the inherent tendency of the connection element to expand creates the connection between the component and the connection element. Accordingly, the installation requires a high force effort for inserting the connection element into a component opening. Furthermore, especially the high connection forces applied by the connection element, for example in the radial direction, cause that creeping, setting and flowable materials are modified under these mechanical stresses or loads to the disfavor of the connection. The materials yield namely so that the connection strength between this spring strong connection element and the component is weakened. A further disadvantage is that the described connection element has to be adapted in its radial and axial size to the component opening, like a screw. Because due to the rigid and inflexible wire coil in at least the central region of the connection element no adaption to changed component geometries can be achieved by changing the geometry of the connection element.
A fastening clamp is described in DE 31 47 430 A1. This clamp is made of a wire that is wound into a spiral spring-like wire coil with a head-shaped spiral collar. In adaptation to a component opening into which the fastening clamp is to be used for connecting at least two components, the wire coil is made smaller in its outer diameter than the inner diameter of the bore. It follows that this fastening clamp does not fasten two parts at each other by a radially acting press fit. Rather, this fastening clamp has a hook at its axial end opposite to the spiral collar so that the fastening clamp fastens at least two components between the hook and the spiral collar at each other by tension. Specifically, the fastening clamp can only be installed in through holes. There, the hook is moved away from the wire coil in axial direction so far that it can hook at the opposite component wall at the output of the component bore outside of the bore.
Thus, this fastening clamp is disadvantageously only applicable in through holes. In addition, the hook extends in radial direction beyond the wire coil, which makes an adaption of the space necessary which is required for installation. A further disadvantage is that this fastening clamp cannot prevent radial movement of the components with respect to the wire coil.
Starting from the connection elements described above there is, thus, a need to provide a flexibly usable connection element of simplified manufacturing and installation compared to the prior art.